1. Field of the Invention
The present invention relates to a PNA chip using zip-codes and to a method for fabricating the same. More particularly, the invention relates to a PNA zip-code chip in which PNA zip-code probes are immobilized at high density using an epoxy compound as a linker, as well as to a method for fabricating the same.
2. Background of the Related Art
As large amounts of genetic information are developed as a result of genome projects involving various organisms, including human genome projects, studies to interpret such genetic information and to analyze the relation thereof are actively being conducted. The focus of studies in the fields of molecular biology and bioengineering is changing from the structural interpretation of DNA to the functional interpretation of genes and the identification of the relation between genes. As a result of this change, various methods for analyzing genetic information are now developed. In particular, DNA chips are attracting attention as a means of analyzing a sample more effectively using the huge amounts of genetic information resulting from genome projects, since such chips can analyze such huge amounts of genetic information in a short time, and their use is easily automated.
A DNA chip is a chip in which 1,000-1,000,000 oligonucleotides, each containing 8-25 bases, are arranged and attached on a solid surface, such as silicon, surface-modified glass, polypropylene or activated polyacrylamide. DNA to be immobilized on the chip is determined depending on the DNA base sequence of a target gene. This DNA chip has various applications comparable to recombinant gene technology and polymerase chain reaction (PCR), and also possesses advantages surpassing the prior technology. The DNA chip can be applied to a wide range of subjects, depending on the way it is used, and thus has a wide range of application fields. The use of the DNA chip makes it possible to analyze even a very small amount of a sample and to identify the base sequences of a target gene at various sites at the same time.
A DNA analysis system utilizing the DNA chip is expected to quicken the speed of DNA analysis by tens to hundreds of times, thus greatly shortening the completion time of the genome projects of various organisms that are currently being conducted and greatly lowering the current unit cost of analysis per base. Such DNA analysis system is applicable to a wide range of fields, including the diagnosis of congenital diseases, the investigation of mutations, cancer diagnosis, the detection of pathogenic bacteria, the analysis of gene expression, and the development of new drugs.
A DNA chip with zip-codes (Gerry, N. P. et al., J. Mol. Biol., 292:251, 1999; Hirschhorn, J. N., Proc. Natl. Acad. Sci., 97:12164, 2000) is fabricated by immobilizing probes with a given length of base sequences having no homology with each other on a solid substrate and designing the base sequence of a target DNA to be hybridized on the chip in such a manner that the 5′-terminal end of the target gene has a base sequence complementary to the probes and the 3′-terminal end has a base sequence complementary to the gene. Thus, the DNA chip has advantages, in that it can be fabricated in a simple manner and it can obtain diagnostic results on the same chip by reconstructing the base sequence site of a target DNA to match with a gene without a separate process for constructing probes.
PNA, an analog of DNA, has a peptide bond as a flame and contains four kinds of bases as in DNA. Unlike DNA, PNA bears no negative charge at the frame (Nielsen, P. E. et al., Sci., 254:1497, 1991). FIG. 1 shows the structure of DNA having a sugar-phosphate flame and the structure of PNA having a peptide bond frame. PNA has a higher stability than DNA against nuclease and various chemicals, and is more stable than DNA in a wide range of temperature and pH. PNA forms strong bonds with DNA and RNA and has a higher specificity and selectivity than DNA (Nielsen, P. E Acc. Chem.Res., 32:624, 1999). As a result, PNA is useful in many applications, including antigen-antibody reaction, hybridization technology and drug delivery (Dean, D. A., Adv. Drug Delivery Rev., 44:81,2000).
DNA chips developed to date are fabricated by cumbersome processes in which the base sequences of probes immobilized on the chip match with the target DNA, depending on the kinds of base mutations or SNPs to be diagnosed. In other words, probes constituting the DNA chip must be reconstructed depending on the type of target DNA to be diagnosed, which is troublesome and increases the fabrication cost of the chip.